Are pressure pop-offs beneficial to the bladder in boys with posterior urethral valves?

Abstract

Pressure pop-offs, such as high-grade vesicoureteral reflux with renal dysplasia, have historically been considered beneficial for renal and bladder outcomes in boys with posterior urethral valves (PUV). Recent longer-term studies have called into question the beneficial effects of pop-offs on renal function. To evaluate how pop-offs affect bladder outcomes in boys with PUV. At a single-center, the electronic medical records of boys with PUV who underwent valve ablation from 2000 to 2014 were retrospectively reviewed for bladder and continence outcomes. Patients were excluded due to presentation after one year of age, age at last follow-up <1 year, lack of urodynamic study (UDS), lack of voiding cystourethrogram, or concomitant prune belly syndrome. Between patients with and without pop-offs, the following outcomes were compared: prevalence of significant hydronephrosis (Society for Fetal Urology grade 3 or 4) prior to valve ablation and at last follow-up, nadir creatinine level, classification of initial UDS, type of medical and/or surgical interventions, dryness during the day and toilet-training status at last follow-up (among patients ≥4 years), and age at toilet-training. For patients with multiple UDS, initial and latest UDS were compared. 48 patients met inclusion criteria, of whom 31 (65%) had pop-offs and 17 (35%) did not. Median age at last follow-up was 5.9 years (range: 1.0-12.2 years). Patients with pop-offs were more likely to have unsafe initial UDS (26% vs. 12%, p=0.15) but less likely to have high voiding pressures at their latest UDS (15% vs. 50%, p=0.03). Patients with pop-offs were more likely to have used clean intermittent catheterization (26% vs. 0%, p=0.04) and were less likely to be toilet-trained by age 4 (76% vs. 100%, p=0.15) or dry during the day at last follow-up (56% vs. 92%, p=0.06). Toilet-trained patients with pop-offs were toilet-trained by an earlier age than patients without pop-offs (3 vs 4 years, p=0.04). The results of the present retrospective study show that patients with pop-offs required more extensive interventions to achieve continence, and achieved continence and toilet-training less frequently than patients without pop-offs. Additionally, our results demonstrated that patients with pop-offs had worse bladder dynamics initially, which may suggest that pop-offs are a manifestation of more excessive pressure build-up prior to valve ablation. Among boys with posterior urethral valves who present in the first year of life, pop-offs do not appear to impart significant benefit to bladder outcomes and may indicate more severe bladder dysfunction.